Method of forming integrated circuit with conductive line having line-ends

ABSTRACT

A method of fabricating a semiconductor integrated circuit (IC) is disclosed. A dielectric layer is deposited over a substrate and a hard mask (HM) layer is deposited over the dielectric layer. A line-like opening is formed in the HM layer and a line-end opening are then formed in the HM layer to connect to the line-like opening at the end of the line-like opening. The dielectric layer is etched through the line-like opening and the line-end opening to form a dielectric trench and a conductive line is formed in the dielectric trench.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC design and materials have produced generations of ICs where each generation has smaller and more complex circuits than previous generations. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.

This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of IC processing and manufacturing. For these advances to be realized, similar developments in IC processing and manufacturing are needed. When a semiconductor device such as a metal-oxide-semiconductor field-effect transistor (MOSFET) is scaled down through various technology nodes, interconnects of conductive lines and associated dielectric materials that facilitate wiring between the transistors and other devices play a more important role in IC performance improvement. Although existing methods of fabricating IC devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a flowchart of an example method for fabricating a semiconductor integrated circuit (IC) constructed according to various aspects of the present disclosure.

FIG. 2 is a cross-sectional view of an example semiconductor device precursor according to the method of FIG. 1.

FIGS. 3A and 3B are cross-sectional views of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1.

FIG. 4A is a top schematic view of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1.

FIGS. 4B and 4C are cross-sectional views of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1. FIGS. 4D and 4E are flowcharts of example methods for fabricating features of an IC according to various aspects of the present disclosure.

FIGS. 5A and 5C are top schematic views of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1.

FIGS. 5B and 5D are cross-sectional views of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1. FIGS. 5E and 5F are flowcharts of example methods for fabricating features of an IC according to various aspects of the present disclosure.

FIGS. 6A and 7A are top schematic views of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1.

FIGS. 6B and 7B are cross-sectional views of an example semiconductor integrated circuit (IC) at fabrication stages constructed according to the method of FIG. 1. FIG. 6C is a flowchart of an example method for fabricating features of an IC according to various aspects of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as being “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

FIG. 1 is a flowchart of one embodiment of a method 100 of fabricating one or more semiconductor devices according to aspects of the present disclosure. The method 100 is discussed in detail below, with reference to a semiconductor device 300 shown in FIGS. 2, 3, 4A-4B, 5A-5C, 6 and 7A-7B for the sake of example. It is understood that additional steps can be provided before, during, and after the method, and some of the steps described can be replaced or eliminated for other embodiments of the method.

Referring to FIGS. 1 and 2, the method 100 begins at step 102 by receiving a semiconductor device precursor 200. The semiconductor device precursor 200 includes a substrate 210. In the present embodiment, the substrate 210 includes silicon. In alternative embodiments, the substrate may include germanium, silicon germanium, gallium arsenide or other appropriate semiconductor materials. Alternatively and for some embodiments, the substrate 210 may include an epitaxial layer. For example, the substrate 210 may have an epitaxial layer overlying a bulk semiconductor. Further, the substrate 210 may be strained for performance enhancement. For example, the epitaxial layer may include a semiconductor material different from those of the bulk semiconductor such as a layer of silicon germanium overlying bulk silicon or a layer of silicon overlying a bulk silicon germanium formed by a process including selective epitaxial growth (SEG). Furthermore, the substrate 210 may include a semiconductor-on-insulator (SOI) structure such as a buried dielectric layer. Also alternatively, the substrate 210 may include a buried dielectric layer such as a buried oxide (BOX) layer, such as that formed by a method referred to as separation by implantation of oxygen (SIMOX) technology, wafer bonding, SEG, or other appropriate methods. In fact various embodiments may include any of a variety of substrate structures and materials.

The semiconductor device precursor 200 may also include various isolation features 220. The isolation features 220 separate various device regions in the substrate 210. The isolation features 220 include different structures formed by using different processing technologies. For example, the isolation features 220 may include shallow trench isolation (STI) features. The formation of a STI may include etching a trench in the substrate 210 and filling in the trench with insulator materials such as silicon oxide, silicon nitride, or silicon oxynitride. The filled trench may have a multi-layer structure such as a thermal oxide liner layer with silicon nitride filling the trench. A chemical mechanical polishing (CMP) may be performed to polish back excessive insulator materials and planarize the top surface of the isolation features 220.

The semiconductor device precursor 200 also includes one or more first conductive features 230. In one embodiment, the first conductive feature 230 may include high-k/metal gates (HK/MGs), a three-dimension HK/MGs wrapping over a fin-like structure. As an example, the HK/MGs may include a gate dielectric layer and metal gate (MG). The gate dielectric layer may include LaO, AlO, ZrO, TiO, Ta₂O₅, Y₂O₃, SrTiO₃ (STO), BaTiO₃ (BTO), BaZrO, HfZrO, HfLaO, HfSiO, LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO₃ (BST), Al₂O₃, Si₃N₄, oxynitrides (SiON), or other suitable materials. The MG may include a single layer or multi layers, such as a metal layer, a liner layer, a wetting layer, and an adhesion layer. The MG may include Ti, Ag, Al, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN, TaN, Ru, Mo, Al, WN, Cu, W, or any suitable materials. Additionally, sidewall spacers (not shown) are formed on the sidewalls of the HK/MGs.

In another embodiment, the first conductive features 230 include electrodes, capacitors, resistors or a portion of a resistor. In yet another embodiment, the first conductive features 230 include a portion of the interconnect structure. For example, the first conductive features 230 include contacts, metal vias, or metal lines.

The semiconductor device precursor 200 also includes second conductive features 240 in the substrate 210. A top surface to the second conductive feature 250 may not be at a same horizontal level as a top surface of the first conductive feature 230. In one embodiment, the second conductive features 240 include doped regions (such as sources or drains). In another embodiment, the second conductive features 240 include electrodes, capacitors, resistors or a portion of a resistor, or a portion of the interconnect structure.

The semiconductor device precursor 200 also includes a first dielectric layer 250 deposited over the substrate 210, including between/over each of the first conductive features 230 and over the second conductive features 240. The first dielectric layer 250 includes silicon oxide, silicon nitride, oxynitride, a dielectric material having a dielectric constant (k) lower than thermal silicon oxide (therefore referred to as low-k dielectric material layer), or other suitable dielectric material layer. The first dielectric layer 250 includes a single layer or multiple layers. A CMP may be performed to remove excessive the first dielectric layer 250 to expose the top surface of the first conductive features 230, as well as to provide a substantially planar top surface for the first conductive features 230 and the first dielectric layer 250.

The semiconductor device precursor 200 also includes a second dielectric layer 260 over the first conductive features 230 and the first dielectric layer 250. The second dielectric layer 410 is similar in many respects to the first dielectric layer 250 discussed above.

The semiconductor device precursor 200 also includes conductive plugs 270 in the first and second dielectric layers, 250 and 260, to form full contacts extending down to the first and the second conductive features, 230 and 240. The conductive plugs 270 are formed along a first direction. The conductive plugs 270 may include copper (Cu), aluminum (Al), tungsten (W), copper or copper alloy, such as copper magnesium (CuMn), copper aluminum (CuAl) or copper silicon (CuSi), or other suitable conductive material. In some cases, the conductive plug 270 is referred to as a metal plug.

Referring to FIGS. 1 and 3, once the semiconductor device precursor 200 is received, the method 100 proceeds to step 104 by depositing a third dielectric layer 310 over the second dielectric layer 260, including over the conductive plugs 270, and a hard mask (HM) layer 320 over the third dielectric layer 310. The third dielectric layer 310 is similar in many respects to the first dielectric layer 250 discussed above in association with FIG. 2.

The HM layer 320 includes silicon nitride, silicon oxide, silicon carbide, titanium oxide, titanium nitride, tantalum oxide, tantalum nitride, or any suitable materials. In addition, the HM layer 320 may include a single layer or multiple layers. The HM layer 320 is different from the third dielectric layer 310 to achieve etching selectivity during a subsequent etch, which will be described later. The HM layer 320 may be deposited by suitable techniques, such as CVD, or physical vapor deposition (PVD). In one embodiment, the HM layer 320 includes a stack of layers: a bottom titanium nitride layer deposited over the third dielectric layer 310; an anti-reflection coating (ARC) layer deposited over the bottom titanium nitride layer and a top titanium nitride layer deposited over the ARC layer, as shown in FIG. 3B.

Referring to FIGS. 1 and 4A-4B, the method 100 proceeds to step 106 by forming a first opening 410 on the HM layer 320. The first opening 410 has a first length L₁ landing in a plane, which is perpendicular to the first direction, and a first width W₁. In the present embodiment, the first length L₁ is defined by two line-ends 412 and is substantially larger than the first width W₁. Therefore, in some cases, the first opening 410 is referred to as a line-like opening. The first opening 410 is aligned to a subset of the conductive plugs 270, now labeling them with the reference number 270A. The first opening 410 may be formed by a procedure (shown in FIG. 4D) that includes depositing a resist layer, forming a first resist pattern on the resist layer (block 450), and etching the HM layer 320 using the first resist pattern as an etch mask (block 452). The first resist pattern is then removed by wet stripping or plasma ashing (block 454). In one embodiment, the first openings 410 are formed by removing the top titanium nitride layer of the HM stack 320 using the first resist pattern as an etch mask, as shown in FIG.4C and FIG. 4E (blocks 460, 462, and 464).

Referring to FIGS. 1 and 5A-5C, the method 100 proceeds to step 108 by forming a second opening 510 on the HM layer 320, landing in the same place as (or near to) where the first opening 410 landed. In the present embodiment, the second opening 510 fully contacts, or overlaps with, the first opening 410 at the line-ends 412. Thus, the second opening 510 forms a new line-end 512 for the first opening 410. In other words, with the second opening 510, the line-end 412 is replaced by the new line-ends 512. The second opening 510 has a second length L₂ along the same direction as the first length L₁ and a second width W₂ along the same direction as the first width W₁. The second length L₂ is substantially smaller than the first length L₁. The second width W₂ is same or larger than the first width W₁. In some cases, the second opening 510 is referred to as a line-end opening.

In one embodiment, the second width W₂ is larger than the first width W₁ and the second opening 510 locates symmetrically to the first opening 410 at the line-end 412 (as shown in FIG. 5A). In another embodiment, the second width W₂ is larger than the first width W₁ and the second opening 510 locates asymmetrically to the first opening 410 at the line-end 412 (as shown in FIG. 5C). In some embodiments, the second opening 510 has a rectangular shape.

As shown in FIG. 5E, the second openings 510 may be formed similar in many respects to the first opening 410 discussed above in association with FIGS. 4A and 4B, which includes forming a resist layer over the HM layer 320 and the first opening 410, forming a second resist pattern on the resist layer (block 550) and etching the HM layer 320 using the second resist pattern as an etch mask (block 552). The second resist pattern is then removed by wet stripping or plasma ashing (block 554). In one embodiment, the second openings 510 are formed by removing the top titanium nitride layer of the HM stack 320 using the second resist pattern as an etch mask, as shown in FIG. 5D and FIG. 5F (blocks 560, 562, and 564).

Referring to FIGS. 1 and 6A-6B, the method 100 proceeds to step 110 by foiming a dielectric trench 610 to expose the conductive plugs 270A. In the present embodiment, the dielectric trench 610 is formed by etching the third dielectric layer 310 using the HM layer 320 with the first and the second openings, 410 and 510, as an etch mask. In one embodiment, the etch process selectively removes the third dielectric layer 310 but substantially does not etch the HM layer 320. Therefore the dielectric trench 610 carries a profile of a combination of the first and the second openings, 410 and 510. In another embodiment (shown in FIG. 6C), using the HM layer 320 with the first and the second openings, 410 and 510, in the top titanium nitride layer of the HM stack 320 as an etch mask, the dielectric trench 610 is formed by etching the ARC layer (block 650), the bottom titanium nitride layer (block 652) and the third dielectric layer 310 (block 654).

The dielectric trench 610 has a line-like portion 612 and a line-end portion 614. The line-end portion 614 has the second width W₂, which is equal or larger than the first width W₁ of the line portion 612. In one embodiment, the second width W₂ is larger than the first width W₁ and the line-end portion 614 located symmetrically to the line-like portion 612. In another embodiment, the second width W₂ is larger than the first width W₁ and the line-end portion 614 locates asymmetrically to the line-like portion 612.

Referring to FIGS. 1 and 7A-7B, the method 100 proceeds to step 112 by filling in the dielectric trench with conductive materials and forming a conductive line 710. In one embodiment, a barrier layer is filled in the dielectric trench 610 first by a proper deposition technique, such as PVD and CVD. The barrier layer may include a metal and is electrically conductive but does not permit (or reduces) inter-diffusion and reactions between the third dielectric material layer 310 and the conductive material to be filled in the dielectric trench 610. The barrier layer may include refractory metals and their nitrides. In various examples, the barrier layer includes TiN, TaN, Co, WN, TiSiN, TaSiN, or combinations thereof. The barrier layer may include multiple films.

The conductive material 710 then fills in the dielectric trench 610, as well as over the barrier layer. The conductive material 710 may include copper (Cu), aluminum (Al), tungsten (W), copper or copper alloy, such as copper magnesium (CuMn), copper aluminum (CuAl) or copper silicon (CuSi), or other suitable conductive material. The conductive material 710 may be deposited by y PVD, CVD, metal-organic chemical vapor deposition (MOCVD), or plating. A recess is then performed to etch back the excessive conductive material 710, as well as the excessive barrier layer, to form the conductive line 710 and a substantial planar surface with the third dielectric layer 310. For example, the recess is performed by chemical mechanical polishing (CMP).

Referring again to FIG. 7A, in the present embodiment, the conductive line 710 carries the profile of the dielectric trench 610 and has a line portion 712 and a line-end portion 714. The line-end portion 714 has the second width W₂, which is equal or larger than the first width W₁ of the line portion 712. In one embodiment, the second width W₂ is larger than the first width W₁ and the line-end portion 714 located symmetrically to the line portion 712. In another embodiment, the second width W₂ is larger than the first width W₁ and the line-end portion 714 locates asymmetrically to the line portion 712.

Additional steps can be provided before, during, and after the method 100, and some of the steps described can be replaced, eliminated, or moved around for additional embodiments of the method 100. The device 300 may undergo further CMOS or MOS technology processing to form various features and regions.

Based on the above, the present disclosure offers a method for fabricating a semiconductor device. The method employs forming a patterned hard mask having two openings. One is a line-like opening and another one is a line-end opening connecting with the line-like opening. The line-end opening has an equal or larger width than a width of the line-like opening. The two openings are formed separately. The method also employs transferring the two-opening profile to a profile of a conductive line. Thus, the conductive line has the equal or larger width of its line end than a width of its width of the line. The method provides a solution for metal-line-end-narrowing issue. The method demonstrates an integration of interconnection with a relaxed process constrains, enhanced electrical short protection and improved process window.

The present disclosure provides many different embodiments of fabricating a semiconductor IC that provide one or more improvements over existing approaches. In one embodiment, a method for fabricating a semiconductor integrated circuit (IC) includes forming a dielectric layer over a substrate, forming a hard mask (HM) layer over the dielectric layer, forming a line-like opening in the HM layer and the line-like opening having ends. The method also includes forming line-end openings in the HM layer to connect with the line-like opening at the end of the line-like opening, etching the dielectric layer through the line-like opening and the line-end opening to form a dielectric trench and forming a conductive line in the dielectric trench.

In another embodiment, a method for fabricating a semiconductor IC includes providing conductive features in a substrate. The conductive features are separated by a first dielectric layer. The method also includes forming a second dielectric layer over the first dielectric layer, including over the conductive features, forming a hard mask (HM) layer over the second dielectric layer, forming a line-like opening in the HM layer. The line-like opening aligns to a subset of the conductive features. The method also includes forming line-end openings in the HM layer to connect with the line-like opening at the end of the line-like opening, etching the second dielectric layer through the line-like opening and the line-end opening to form a dielectric trench and expose the subset of the conductive features. The method also includes forming a conductive line in the dielectric trench to connect to the subset of conductive features. The conductive line carries a profile of the dielectric trench.

In yet another embodiment, a semiconductor device includes a plurality of conductive features over a substrate, a dielectric layer separating the conductive features, a conductive line connecting a subset of the conductive features. The conductive line includes a line-like portion having a first length and a first width and a line-end portion connecting to an end of the line-like portion. The line-end portion has a second width, equal to or larger than the first width. The line-end portion has a second length, which is smaller than the first length.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method for fabricating a semiconductor integrated circuit (IC), the method comprising: forming a dielectric layer over a substrate; forming a hard mask (HM) layer over the dielectric layer; forming, via a first removal process, a line-like opening in the HM layer, the line-like opening having ends and a first width; forming, via a second removal process subsequent to the first removal process, two line-end openings in the HM layer that each connect with the previously-formed line-like opening at the respective ends of the line-like opening, each of the two line-end openings having a second width greater than the first width; etching the dielectric layer through the line-like opening and the line-end openings to form a dielectric trench and expose a set of conductive features, each of the two line-end openings being aligned with a respective conductive feature in the set of conductive features; and forming a conductive line in the dielectric trench.
 2. The method of claim 1, wherein the forming of the line-like opening includes: forming a first photoresist pattern over the HM layer; etching the HM layer through the first photoresist pattern to form the line-like opening with line ends; and stripping the first photoresist pattern.
 3. The method of claim 2, wherein the forming of the line-end openings includes: forming a second photoresist pattern over the HM layer and the line-like opening, aligning to the line ends of the line-like opening; etching the HM layer through the second photoresist pattern; and stripping the second photoresist pattern.
 4. The method of claim 1, wherein the forming the dielectric trench includes: selectively etching the dielectric layer through the HM layer having the line-like opening and the line-end openings, wherein the selective etch has selectivity with respect to the HM layer.
 5. The method of claim 4, wherein the dielectric trench is formed to carry a combination of profiles of the line-like opening and the line-end openings.
 6. The method of claim 1, wherein the forming the conductive line includes: filling in the dielectric trench with a conductive material; and removing excessive conductive material.
 7. The method of claim 6, wherein the conductive line carries a profile of the dielectric trench.
 8. A method for fabricating a semiconductor integrated circuit (IC), the method comprising: providing conductive features, separated by a first dielectric layer, in a substrate; forming a second dielectric layer over the first dielectric layer, including over the conductive features; forming a hard mask (HM) layer over the second dielectric layer; forming a line-like opening in the HM layer, aligned to a first subset of the conductive features, wherein forming the line-like opening is performed using a first photoresist pattern disposed over the HM layer, wherein the line-like opening has a first width; forming a line-end opening in the HM layer to connect with the line-like opening at an end of the line-like opening, wherein forming the line-end opening is performed using a second photoresist pattern disposed over the HM layer, the second photoresist pattern being different than the first photoresist pattern, wherein the line-end opening has a second width, greater than the first width, the line-end opening being aligned to a second subset of the conductive features; etching the second dielectric layer through the line-like opening and the line-end opening to form a dielectric trench and expose the first and second subsets of the conductive features; and forming a conductive line in the dielectric trench to connect to the subset of conductive features, wherein the conductive line carries a profile of the dielectric trench.
 9. The method of claim 8, wherein the HM layer includes a stack of layers, which has: a bottom titanium nitride layer over the second dielectric layer; anti-reflection coating (ARC) layer over the bottom titanium nitride layer; and a top titanium nitride layer over the ARC layer.
 10. The method of claim 9, wherein the forming the line-like opening includes: forming the first photoresist pattern over the top titanium nitride layer; etching the top titanium nitride layer through the first photoresist pattern to form the line-like opening with line end; and stripping the first photoresist pattern.
 11. The method of claim 9, wherein the forming the line-end opening includes: forming the second photoresist pattern over the top titanium nitride layer and the line-like opening, aligning to the line ends of the line-like openings; etching the top titanium nitride layer through the second photoresist pattern; and stripping the second photoresist pattern.
 12. The method of claim 9, wherein the forming the dielectric trench includes: etching the ARC layer, the bottom titanium nitride layer and the second dielectric layer through the top titanium nitride layer having the line-like opening and the line-end opening, wherein the dielectric trench carries a combination of profiles of the line-like opening and the line-end opening.
 13. A method for fabricating a semiconductor device, the method comprising: forming a plurality of conductive features over a substrate; depositing a first dielectric layer between the conductive features; depositing a second dielectric layer over the first dielectric layer; depositing a hard mask (HM) layer over the second dielectric layer; forming a conductive line in the second dielectric layer and connecting a subset of the conductive features, the conductive line including a line-like portion having a first length and a first width and two line-end portions connecting to respective ends of the line-like portion, wherein forming the conductive line includes: forming a line-like opening in the HM layer, aligned to the subset of the conductive features, wherein forming the line-like opening is performed using a first photoresist pattern disposed over the HM layer; forming two line-end openings in the HM layer that each connect with the line-like opening at respective ends of the line-like opening, wherein forming the line-end opening is performed using a second photoresist pattern disposed over the HM layer, the second photoresist pattern being different than the first photoresist pattern; etching the second dielectric layer through the line-like opening and the line-end openings to form a dielectric trench and expose the subset of the conductive features aligned with the line end openings; and filling the dielectric trench with conductive material to form the line-like portion and the line-end portions of the conductive line; wherein the line-end portions have a second width, equal to or larger than the first width, and wherein the line-end portions have a second length, smaller than the first length.
 14. The method of claim 13, wherein the line-end portions of the conductive line, having a larger width than the width of the line-like portion, are symmetric with the line-like portion.
 15. The method of claim 13, wherein the line-end portions have a rectangular shape. 